Asshole
ass·hole
[as-hohl] Show IPA
noun Vulgar.
1.
anus.
Um, actually, Gui isn't "the opening at the lower end of the alimentary canal, through which the solid refuse of digestion is excreted." In a metaphorical sense, he does excrete the refuse of digestion, but he is in no way part of the alimentary canal.
Hopefully you weren't hoping of becoming a lady proctologist, Dr. Dictionary.